Final answer:
The community health nurse in a mobile clinic should prioritize the client with severe chest pain, as it could be a sign of a cardiac event requiring urgent care.
Step-by-step explanation:
In a mobile health care clinic, the community health nurse should assess clients based on the severity and urgency of their symptoms. Among the options given, the nurse should assess the client complaining of severe chest pain first.
This is because severe chest pain could be indicative of a life-threatening condition such as a heart attack or other cardiac events, which require immediate attention. The clients with a minor skin rash, history of hypertension, and those seeking routine vaccinations can be seen afterwards, as these conditions typically do not present immediate risk to life.